support sending capability specific error codes

server/routers/aiGateway/pipeline.ts

@@ -366,10 +366,6 @@ async function resolveTarget(host: string): Promise<ResolvedTarget | null> {
                 .where(eq(resourceAiModels.resourceId, resourceRow.resourceId))
         ]);
 
-        if (attachmentRows.length === 0) {
-            return null;
-        }
-
         return {
             resourceId: resourceRow.resourceId,
             siteResourceId: null,
@@ -427,10 +423,6 @@ async function resolveTarget(host: string): Promise<ResolvedTarget | null> {
                 )
         ]);
 
-        if (attachmentRows.length === 0) {
-            return null;
-        }
-
         return {
             resourceId: null,
             siteResourceId: siteResourceRow.siteResourceId,
@@ -756,6 +748,14 @@ export async function handleAiGatewayProxy(
             });
         }
 
+        if (attachments.length === 0) {
+            return res.status(HttpCode.FORBIDDEN).json({
+                error: {
+                    message: "No AI providers configured for this resource"
+                }
+            });
+        }
+
         const capableAttachments = attachments.filter((a) =>
             providerHasCapability(a.provider.capabilities, capability)
         );